org.springframework.integration.handler.LambdaMessageProcessor.java Source code

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Here is the source code for org.springframework.integration.handler.LambdaMessageProcessor.java

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/*
 * Copyright 2016-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.integration.handler;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.integration.context.IntegrationContextUtils;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHandlingException;
import org.springframework.messaging.converter.MessageConverter;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;

/**
 * The {@link MessageProcessor} implementation for method invocation on the single method classes
 * - functional interface implementations.
 *
 * @author Artem Bilan
 * @author Gary Russell
 *
 * @since 5.0
 */
public class LambdaMessageProcessor implements MessageProcessor<Object>, BeanFactoryAware {

    private static final Log logger = LogFactory.getLog(LambdaMessageProcessor.class); // NOSONAR lower case static

    private final Object target;

    private final Method method;

    private final Class<?> payloadType;

    private final Class<?>[] parameterTypes;

    private MessageConverter messageConverter;

    public LambdaMessageProcessor(Object target, Class<?> payloadType) {
        Assert.notNull(target, "'target' must not be null");
        this.target = target;
        final AtomicReference<Method> methodValue = new AtomicReference<>();
        ReflectionUtils.doWithMethods(target.getClass(), methodValue::set, methodCandidate -> {
            boolean isCandidate = !methodCandidate.isBridge() && !methodCandidate.isDefault()
                    && methodCandidate.getDeclaringClass() != Object.class
                    && Modifier.isPublic(methodCandidate.getModifiers())
                    && !Modifier.isStatic(methodCandidate.getModifiers());
            if (isCandidate) {
                Assert.isNull(methodValue.get(), "LambdaMessageProcessor is applicable for inline or lambda "
                        + "classes with single method - functional interface implementations.");
            }
            return isCandidate;
        });

        Assert.notNull(methodValue.get(), "LambdaMessageProcessor is applicable for inline or lambda "
                + "classes with single method - functional interface implementations.");

        this.method = methodValue.get();
        this.method.setAccessible(true);
        this.parameterTypes = this.method.getParameterTypes();
        this.payloadType = payloadType;
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.messageConverter = beanFactory.getBean(
                IntegrationContextUtils.ARGUMENT_RESOLVER_MESSAGE_CONVERTER_BEAN_NAME, MessageConverter.class);
    }

    @Override
    public Object processMessage(Message<?> message) {
        Object[] args = buildArgs(message);

        try {
            return this.method.invoke(this.target, args);
        } catch (InvocationTargetException e) {
            if (e.getTargetException() instanceof ClassCastException) {
                logger.error(
                        "Could not invoke the method due to a class cast exception, if using a lambda in the DSL, "
                                + "consider using an overloaded EIP method that takes a Class<?> argument to explicitly "
                                + "specify the type. An example of when this often occurs is if the lambda is configured to "
                                + "receive a Message<?> argument.",
                        e.getCause());
            }
            throw new MessageHandlingException(message, e.getCause());
        } catch (Exception e) {
            throw new MessageHandlingException(message, e);
        }
    }

    private Object[] buildArgs(Message<?> message) {
        Object[] args = new Object[this.parameterTypes.length];
        for (int i = 0; i < this.parameterTypes.length; i++) {
            Class<?> parameterType = this.parameterTypes[i];
            if (Message.class.isAssignableFrom(parameterType)) {
                args[i] = message;
            } else if (Map.class.isAssignableFrom(parameterType)) {
                if (message.getPayload() instanceof Map && this.parameterTypes.length == 1) {
                    args[i] = message.getPayload();
                } else {
                    args[i] = message.getHeaders();
                }
            } else {
                if (this.payloadType != null
                        && !ClassUtils.isAssignable(this.payloadType, message.getPayload().getClass())) {
                    if (Message.class.isAssignableFrom(this.payloadType)) {
                        args[i] = message;
                    } else {
                        args[i] = this.messageConverter.fromMessage(message, this.payloadType);
                    }
                } else {
                    args[i] = message.getPayload();
                }
            }
        }
        return args;
    }

}